This was a take home project. Scrubbed history to remove any references to the company.

This is a simple camera recorder that exposes a HTTP REST API as the control surface.

Development

System Requirments

• Linux (Tested on Pop!_OS 22.04 LTS)
• Rust 1.7.0 or later
• gstreamer 1.22.0 or later

Build, Test, Run

cargo build --bin recorder

cargo test --package recorder -- --nocapture

cargo run -- <command line options>

USAGE:
    recorder 0.1.0

USAGE:
    recorder --host <HOST> --port <PORT>

FLAGS:
        --help       Prints help information
    -V, --version    Prints version information

OPTIONS:
    -h, --host <HOST>    Sets the host to connect to
    -p, --port <PORT>    Sets the port to connect to

API

All API calls use the Content-Type: application/json header.

Start Recording

This is a blocking call. It will return when the GST pipeline has entered into PLAYING state, or if an error occurs.

Returns

• 200 OK if successful
• 400 Bad Request if the request failed.

POST http://.../start
{
    "duration": <unsigned int>, // Optional. Default: infinite
    "input": { // Optional.
        "name": <string>,
        "variant": <object> // Optional. Default: "v4l2"
    },
    "encoder": { // Optional.
        "name": <string>,
        "variant": <object> // Optional. Default: "X265"
    },
    "output": {
        "name": <string>,
        "variant": <object> // Optional. Default: "filesink"
    }
}

Example

{
    "name": "Recordcer",
    "duration": 5,
    "input": {
        "name": "V4L2",
        "variant": {
            "V4l2": {
                "device": "/dev/video4"
            }
        }
    },
    "encoder": {
        "name": "X265",
        "variant": {
            "X265": {
                "bitrate": 5000
            }
        }
    },
    "output": {
        "name": "FileSink",
        "variant": {
            "FileSink": {
                "muxer_config": {
                    "Matroska": {

                    }
                },
                "location": "/tmp/timed.mkv"
            }
        }
    }
}

Stop Recording

This is a blocking call. It will return when the GST pipeline has processed the EOS event.

Returns

• 200 OK if successful
• 400 Bad Request if the request failed.

POST http://.../stop

Input Configurations

• V4L2

{
    "V4l2": {
        "device": <string>, // Default: "/dev/video0"
    }
    
}

• Test Source

{
    "Test" {
        "pattern": <string>, // ["smpte", "snow", "black", "white", "red", "green", "blue", "checkers1", "checkers2", "checkers4", "checkers8", "circle", "smpte75", "zoneplate", "gamut", "chroma-zoneplate", "solid-color", "ball", "smpte100", "bar", "pinwheel", "spokes", "gradient", "colors", "bar", "pinwheel", "spokes", "gradient", "colors"]. Default: "smpte"
    }
}

Encoder Configurations

{
    "X264": {
        "bitrate": <unsigned int>, // Default: 1000000
        ... // See src/encoder/x264enc.rs Config for more options
    }
    // OR
    "X265": {
        "bitrate": <unsigned int>, // Default: 1000000
        ... // See src/encoder/x265enc.rs Config for more options
    }
}

Output Configurations

• File

{
    "FileSink": {
        "location": <string>, // Default: "/tmp/output.mp4"
        ... // See src/output/filesink.rs Config for more options
    }
}

• FakeSink

{
    "FakeSink": {
        ... // See src/output/fakesink.rs Config for options
    }
}

Stop Recording

POST http://.../stop

POST messages have the following 200 OK responses:

{
    "status": "OK",
}

Error responses will have the following format:

{
    "state": "Stopped | Playing | Error", // Not Implemented
    "error_message": String, 
    "error_pipeline_graph": String, //graphviz dot format - Not Implemented
}

Project Notes

• Given the limited time, I have chosen to make a statically linked pipeline. This is a tradeoff between simplicity and flexibility.
• Personally I would have preferred to use /config as an endpoint to configure the pipeline. Reasoning being it is helpful to get errors early while allocation (RAII) is occurring.
• Not all encoders are implemented. Currently only X264 and X265 are implemented.
• Muxer properties are not implemented. Currently just the defaults are used.
• I have taken a slight liberty with some of the code, and used structures from a prior personal project to aid in the speed of development.
• This is a very basic implementation. It is not production ready. It is more along the lines of a proof of concept. For a production system I would focus on architecture and through tests. Error handling would be more robust, and the API would be more flexible.
• There is code smell with respect to configuration of the Encoder. This should be improved.
• There are most certainly bugs in the code (logic and maybe leaks due to reference counting). I have not had time to really test it.

License

Licensed under LGPL 2.1.